Oldest securely dated evidence for a river flowing through the Thar
Desert, Western India

Date:
October 19, 2020
Source:
Max Planck Institute for the Science of Human History
Summary:
Using luminescence dating of ancient river sediments, a new study
presents evidence for river activity at Nal Quarry in the central
Thar Desert starting from approx. 173 thousand years ago. These
findings represent the oldest directly dated phase of river
activity in the region and indicate Stone Age populations lived in a
distinctly different Thar Desert landscape than we encounter today.



FULL STORY ========================================================================== Situated at the threshold of the South Asian monsoon, the Thar Desert
is an important region for understanding how past environmental
change impacted patterns of human migration and adaptation to new
habitats. Recent research highlighting the role of the Thar Desert
in human prehistory has indicated that humans spread eastwards into
the region starting from 114 thousand years ago during a phase of
enhanced monsoonal rainfall, when the desert was transformed into lush grasslands. However, more recent phases of sand dune activity have
obscured these ancient landscapes inhabited by earlier human populations.


==========================================================================
In a new study published in Quaternary Science Reviews, researchers from
The Max Planck Institute for the Science of Human History (MPI-SHH), Anna University, and the Indian Institute of Science, Education and Research
(IISER) Kolkata document evidence for river activity in the central Thar Desert. This evidence indicates a river flowed with phases of activity
dating to approx.

172, 140, 95 and 78 thousand years ago, nearby to Bikaner, which is
over 200 km away from the nearest modern river. These findings predate
evidence for activity in modern river courses across the Thar Desert
as well as dried up course of the Ghaggar-Hakra River. The presence
of a river running through the central Thar Desert would have offered
a life-line to Palaeolithic populations, and potentially an important
corridor for migrations.

Lost Rivers of the Thar Desert Located at the threshold of monsoonal
Asia, the Thar Desert marks the eastern extent of the desert belt that stretches westwards across Arabia and the Sahara. While this desert
belt is typically thought of as inhospitable to early humans, it is
becoming increasingly clear that during humid phases in the past human populations have prospered in these landscapes. This is perhaps best
known in western South Asia from studying the Indus Civilisation (also
known as the Harappan Civilisation) which flourished at the margins of
the Thar Desert along the course of the now-seasonal Ghaggar-Hakra River between 3200-1500 BCE, and is thought to have inspired the mythological Saraswati River mentioned in the Rig Veda.

Yet the potential importance of 'lost' rivers for earlier inhabitants
of the Thar Desert have been overlooked. "The Thar Desert has a rich prehistory, and we've been uncovering a wide range of evidence showing how Stone Age populations not only survived but thrived in these semi-arid landscapes," says Jimbob Blinkhorn of MPISHH. "We know how important
rivers can be to living in this region, but we have little detail on what
river systems were like during key periods of prehistory." Studies of satellite imagery have shown a dense network of river channels crossing
the Thar Desert. "These studies can indicate where rivers and streams
have flown in the past, but they can't tell us when" explains Prof Hema Achyuthan of Anna University, Chennai. "To demonstrate how old such
channels are, we had to find evidence on the ground for river activity
in the middle of the desert." Nal Quarry A deep deposit of river sands
and gravels was studied by the team, which had been exposed by quarrying activity near the village of Nal, just outside of Bikaner. By studying
the different deposits, the researchers were able to document different
phases of river activity. "We immediately saw evidence for a substantial
and very active river system from the bottom of the fluvial deposits,
which gradually decreased in power through time" explained Achyuthan.

"Standing in the middle of the desert, the question we had to answer
was 'How old was this river?'." The researchers used a method called luminescence dating to understand when quartz grains in the river sands
were buried. The results indicated that the strongest river activity at
Nal occurred at approx. 172 and 140 thousand years ago, at a time when
the monsoon was much weaker than today in the region. River activity
continued at the site between 95 to 78 thousand years ago, after which
only limited evidence for the presence of a river at the site, with
evidence for a brief reactivation of the channel 26 thousand years ago.

A life-line in the desert The age of this river flowing in the middle
of the desert is of particular interest. The river was flowing at its
strongest during a phase of weak monsoonal activity in the region, and
may have been a life-line to human populations enabling them to inhabit
the Thar Desert. The timeframe over which this river was active also
overlaps with significant changes in human behaviour in the region,
which have been linked with the earliest expansions of Homo sapiens
from Africa into India. "This river flowed at a critical timeframe for understanding human evolution in the Thar Desert, across South Asia and
beyond" says Blinkhorn, adding "This suggests landscape in which the
earliest members of our own species, Homo sapiens, first encountered
the monsoons and crossed the Thar Desert may have been very different
to the landscape we can see today." The next phase of research is to demonstrate where the river flowed from.

Studies of satellite images have suggested a potential connection with
a Himalayan source, such as the Sutlej. "We can't demonstrate where the
river flowed from at present" says Blinkhorn, adding "but the Indira
Ghandi Canal, sourced from the Sutlej River, gives us some insight into
what happens when a river flows through the centre of the Thar Desert
-- plants and wildlife flourish, providing ideal conditions for early
human populations."

========================================================================== Story Source: Materials provided by Max_Planck_Institute_for_the_Science_of_Human_History.

Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. James Blinkhorn, Hema Achyuthan, Manoj Jaiswal, Atul Kumar
Singh. The
first dated evidence for Middle-Late Pleistocene fluvial activity
in the central Thar Desert. Quaternary Science Reviews, 2020; 250:
106656 DOI: 10.1016/j.quascirev.2020.106656 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/10/201019125524.htm

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